Hydrodynamic coupling device



May 10, 1966 R. c. ZEIDLER HYDRODYNAMIC COUPLING DEVICE 2 Sheets-Sheet lOriginal Filed Nov. 20, 1961 May 10, 1966 R. c. ZEIDLER 3,250,222

HYDRODYNMIC COUPLING DEVICE Original Filed Nov. 20, 1961 2 Sheets-SheetZ 43 H25 y l United States Patent Oli-ice 3,250,222 Patented May 10,1966 3,256,222 HYDRDYNAMlC COUPLIG DEVICE Reinhold C. Zeidler, Detroit,Mich., assignor to Borg- Warner Corporation, Chicago, Ill., acorporation of Illinois Original application Nov. 20, 1961, Ser. No.153,601, now Patent No. 3,138,107, dated .lune 23, 1964. Divided andthis application Dec. 16, 1963, Ser. No. 338,545 1 Claim. (Cl. 10S-111)The present invention is a divisional application of Serial No. 153,601,tiled November 20, 1961, now United States Patent 3,138,107, issued lune23, 1964; and is a continuation-in-part of application Serial No.509,718, filed May 20, 1955, now United States Patent 3,024,735, issuedMarch 13, 1962.

This invention relates to hydrodynamic coupling devices and moreparticularly to housings of such devices providing a toroidal uidcircuit in which are disposed impeller blades and turbine blades,thehousing comprising two substantially semi-toroidal shells with rtheimpeller blades being preferably connected to one of the shells of thehousing, the turbine blades being connected to a separate couplingmember relatively rotatable to the housing.

Hydraulic coupling devices such as uid couplings an torque convertorshave in the past been formed with -two substantially semi-toroidalshells, the shells being respectively formed of aluminum and steel, orboth shells being formed of steel. In assembling aluminum and steelshells, it has been the conventional practice to connect the shells attheir radially outer peripheries with bolts or screwthreaded devices toconnect the aluminum shell to the steel shell in view of the inabilityof welding, or otherwise, connecting, the aluminum shell to the steelshell. This is an expensive operation in view of the necessity offorming screw threads in at least one of the shells to receive thebolts, and providing openings in the other shell to receive the bolts tobe threaded into the first-mentioned shell; -or alternatively, providinga separate screw-threaded ring engaging one of the Shells and threads onthe other shell in order to assemble the shells together. In eithercase, the connection of an aluminum shell to a steel shell involves amultitude of expensive operations, including hand operations, to providethe satisfactory assembly of the shells. It has been found simpler andinexpensive to connect two steel shells together to form the housing, bytelescoping `the two steel shells at their outer peripheries, andproviding a continuous weld between the edge of the outer telescopingmember and the outer surface of the inner -telescoped member to insure asatisfactory connection between the two shells, and to prevent thepossibility of anyleakage of the duid from the housing provided byconnected shells.

In conventional automotive transmission practice, the hydrodynamiccoupling device embodying the housing has one of the shells `thereofusually connected to the crankshaft of the engine, either directly or bya drive plate, and the turbine member of the fluid coupling or torqueconverter is connected to the transmission input shaft, the crankshaftand the transmission being disposed on a common axis and terminating atlixed spaced points on the axis for reception of the hydrodynamiccoupling device therebetween and connection to the shafts. Thus, it isnecessary that `the axial dimension of the device be consistentlymaintained toinsure the proper location between the engine andtransmission and connection to the engine crankshaft and thetransmission input shaft. It has been found by connecting the two shellsforming the fluid-containing housing, by a continuous weld, reduction inthe diameter of the housing occurs adjacent to the weld. This reductionin diameter extends a short distance on either side of the weld and iscaused by the fact that, during the welding operation, the twotelescoped shells adjacent to the weld become highly heated, so thatconsequently, upon cooling, the shrinkage produces a reduction in thediameter. This reduction in the diameter, and particularly where theshell of the housing, connected to the engine crankshaft, is shallowcauses this shell to bulge toward the engine crankshaft and destroys therequired accurate axial dimension of the hydrodynamic coupling devicefor location between and assembly with the engine crankshaft and thetransmission input shaft. This undesirable factor has provided anobstacle, in many cases, to utilizing a housing formed of two shellsprovided with a continuous weld, as described, in the assembly of thetwo shells at the factory, and a condition which is considerablyaggravated in the service field where the two shells of the housing mustbe disconnected and then rewelded after the necessary repairs have beenmade to the hydrodynamic coupling device.

It is the object of the present invention to provide an improvedstructure and assemblies of two shells of a hydrodynamic coupling devicehousing in which the two shells ci the housing may be assembled in aready and facile manner, during the assembly operation withoutdeformation or distortion of the shells and consequent changes in theaxial and diametrical dimensions of the housing.

It is another object of the invention to provide an improved structureand assembly of housings lfor hydrodynamic coupling devices in which thetwo telescoped outer portions of the shells of the housing are connectedto each other while maintaining the original shape of the shells andwithin the predetermined space limits required for assembly of thedevicesl between the engine and the transmission -of an automotivevehicle.

Another object of the invention is to provide a new and improvedstructure and assembly of two shells of a housing of a hydrodynamiccoupling device, having telescoping outer peripheries connected to eachother by welding, or by interlocking portions thereof, to provide aconnection insuring the two shells from disassembly under thecombination of hydraulic static pressure and centrifugal forceencountered in the operation of the hydrodynamic coupling devices.

The invention consists of the novel constructions, arrangements, devicesand methods of assembly to be hereinafter described and claimed forcarrying out the abovestated objects, and such other objects as willappear from the .following description of certain preferred embodimentsillustrated in the accompanying drawings, wherein:

FIG. l is a fragmentary side elevation, partly in section, of ahydraulic torque converter showing a preferred embodiment of theinvention;

FIG. 2 is a fragmentary elevation view, taken along line 2 2 of FIG. l;

FIG. 3 and FIG- 3a illustrate an alternate embodiment of the inventionillustrating the respective parts prior to the assembly thereof;

FIG. 4 and FIG. 4a illustrate another embodiment of the invention;

FIG. S is another embodiment of the invention illustrating a dilferenttype of connection of the two shells of the housing;

FIG. 6 is similar vto FIG. 5, illustrating a dilferent location of theseal ring;

FIG. 7 is a sectional View illustrating another embodiment of theinvention and illustrating `a further type of connection of the twoshells of the housing:

FIG. 8 is a top plan view of the connection shown in FIG. 7, asindicated by the plane S-S of FIG. 7;

FIG. 9 is a View similar to FIG. 7, but illustrating the disposition ofthe shells prior to connecting the shells by a final assembly operation;

FIG. 10 is a view similar to FIG. 7, illustrating'a different locationof the seal ring between the two shells;

FIG. 1l is a sectional view illustrating another embodiment of theinvention;

FIG. 12 is a sectional view bodiment of the invention; and

FIG. 13 is a vfragmentary sectional view of'a housing having its twoshells connected together in accordance with prior art practice.'

Referring now to the drawings and first describing the hydrodynamiccoupling device shown as a hydraulic torque converter in FIG. 1, theconverter comprises a vaned driving element or impeller or pump 10, avaned driven element or turbine 11, and a vaned reaction element orstator 12, the pump functioning t`o impart energy to a body of liquid inthe torque converter, the turbine receiving energy from the liquid, andthe stator being held from rotation and acting to change the directionof the flow of the liquid so that the device functions to multiplytorque.

A one-way brake 13 of the sprag type is disposed between the stator 12and a stationary cylindrical portion 14 of a Vtransmission casing, theone-way brake being op illustratingv a further emerative to preventrotation of the stator in one direction during the torque multiplicationstages of the converter, while permitting rotation of the stator in theopposite direction at what is commonly termed the coupling point of thetorque converter. The vanes of the pump, turbine and stator may be ofthe type illustrated and described in the U.S. Patent 2,663,149, issuedDecember 22, 1953.

The pump 10 is connected to an engine (not shown) having a shaft 15driven thereby and provided with a flange 16 connected by bolts 17 to adrive member 18 connected to the pump 10 for driving the pump. As seenin FIG. 1, the bolts 17 may have their heads spot-welded as at 19 to thedrive plate with the shank of the bolts extending through openings inthe engine shaft flange 16 and being secured thereto by nuts 20. I`heturbine 11 is provided with a hub 21 splined to a driven shaft 22 whichmay be the input shaft of a gear set of a transmission. The impeller 10is provided with a hub rotatably supported upon the cylindrical portion14 of the transmission casing.

The hydraul-ic torque converter is designed to be filled with a liquidfor the ytransmission of torque from the impeller 10 rotated by theengin-e, to the turbine 11 connected to the driven shaft 22. It will beseen from an inspection of FIG. 1 that the impeller 10 is `pro-videdwith a hollow substantially semi-toroidal shell 23 having its radiallyouter periphery defined by an annular portion or cylindrical flan-ge 24,vanes 25 being `disposed between and connected to a core ring 26 and theshell 23. The drive plate 18 is a hollow shell formed with asubstantially semi-toroidal portion provided with a radially outerannular peripheral portion defined by a flange 27 bent relative to thesemi-toroidal portion such that the flange 27 extends toward thesemi-toroidal portion. The flange 27 is adapted to mate with thecylindrical flange 214. The flange 27 is radially inwardly of thecylindrical flange 2A of the shell 23, such that the two flanges extendin opposite directions relative to the axis of rotation A-A of thetorque converter. The semi-torioidal portions of the shells 18 and 23thus define a housing forming a fluid chamber for containing fluid inthe fluid torque converter. The telescoped flange 27 of the shell 18 andthe telescoping flange 24 of the impeller shell 23 are provided withshoulders 28 and 29, respectively having radial surfaces cooperating toengage each other to locate the shells 18 and 23 in a predeterminedaxially spaced relation. T-he flange 27 of the shell 18 is provided withan annular groove 30 receiving a ring O of synthetic or natural rubber,the ring being compressed between the flanges 4 and 27 and providing aseal to prevent the flow of 4 liquid between lthe telescoped flanges andfrom the converter under centrifugal pressure or hydraulic staticpressure forces in the housing `during operation of the converter.

The edge of the cylindrical flange 24 may be secured to the shell 18 inassembly by rolling or spinning the terminal edge of the flange 24 toprovide an inwardly directed continuous lip to prevent axial movement ofthe shells away from each other. Alternatively, the edge off thecylindrical flange 24 may be secured to the shell 18 in assembly by aplurality of circumferentially spaced spot ywelds extending between andconnecting the terminal edge of the flange 24 and the shell 1S. Thismode of assembly prevents the shells from slipping apart under thecombination of hydraulic static pressure and centrifugal force. Thewelding operation takes place quickly and a minimum amount of heat isgener-ated, and, due to the fact that only a small amount of welding isapplied, very little distortion, if any, of the welded parts occurs. Theshells 1S and 23 are formed of sheet steel stampings having their outerannular flanges 24 and 27, respectively, machined accurately to permit aclose slip fit, with the shoulders 28 and 29 in both shells permittingthe shells to engage a predetermined amount so that the overal-l heightof the assembly is maintained. It will be apparent that the small amountof welding accomplished quickly at localized circumferentially spacedportions of the end of the flange 24 and the flange 27, eliminates thepossibility of any distortion of the shells occurring to reduce thediameter of the assembly or to lengthen the axial dimension of thetorque converter.

FIG. 13 illustrates a conventional housing of a hydraulic torqueconverter comprising two shells I and P having telescoping flanges P1,I1 with a continuous weld W between the edge of the flange P1 and theouter surfalce of the flange I1. It has been found, in welding the twoshells together -in the manner described to yformv the torque converterhousing, objectionable rdistortion of the shells occurs as there is areduction -in diameter extending a short distance on either side of theweld causing the shell P to be distorted and to increase its axialdimension as indicated in dotted lines in FIG. 13. This reduction ondiameter of the shells P and I of the converter housing 1s caused by thefact that, during the welding operation, the two shells have theirportions, adjacent to the weld, highly heated and, consequently, uponcooling the shrinkage produces a reduction in diameter of as much as.025 inch with the attendant result that the housing is distorted 1n anaxial' dimension which renders it incapable of beinlg fitted within orlocated in the predetermined axial space allotted to it between anengine and a transmission and connection to the engine crankshaft andtransmission lnput shaft, with the result that the torque converter maynot be suitable for installation in the l-iimited space provided for itbetween the engine and transmission by automobile manufacturers.

It will be seen that, in the assembly of the shells 18 and 23 of thehousing in FIG. 1, the very limited and quick application of heat atcircumferentially spaced points on the edge of the flange 24 and on theflange portion 27 of the shells will prevent any possibility of theshells 18 and 23 being distorted during the assembly operat1on.

FIGURE 3 illustrates another embodiment of the invention affording aconnecting between two shells 18a and 23a, of a torque converterhousing, the shell 18a and the shell 23a having semi-toroidal portions,telescoping radially outer annular portions or flanges 27a and 24a. Theflanges 27a and 24a are provided with abutting shoulders 28a and 29a,similar to the features illustrated in FIG. l. A resilient rubber ringmay be disposed in a groove 30a in the flange 24a for engagement withthe flange 27a of the shell 18a. In this embodiment of the invention,the shell 18a is provided with a plurality of circumferentially spacedindents 32 as shown in FIG. 3a.

The outer terminal edge of the axially extending tlange 27a is providedwith a lip 33 which is adapted to engage the circumterentially spacedindents 32 such that the lip 33 and the indents 32 afford a connectionbetween the shells 18a and 23a.

FIG. 4 illustrates an embodiment similar to the embodiment illustratedin FIG. 3 except that a knurled surface K (FIG. 4a) is provided on theange 27 of the shell 18. This knurled surface provides a connectionbetween the vshell sections which connection is capable of transmittinga higher torque load than the connection illustrated in FIG. 3.

The assembly illustrated in FIGS. 3,. 3a, 4 and 4a of the two shells ofthe housing of the torque converter cannot, in any way, cause distortionof the two shells as the spinning or rolling operation is only effectiveupon the thin outer marginal edge of one shell in engaging the othershell.

FIG. 5 illustrates another embodiment of the invention in which twoopposed hollow shells 1812 and 23b have radially outer annular portionsor anges each formed by angularly related parts extending respectivelyin axial and radial directions. The axially extending parts 34 and 35are in telescoped relation and the radially outwardly extending parts 36and 37 are engaged with each other as clearly shown in FIG. 5, theradially extending .part 37 of the ange .of the shell 18b being bent atright Aangles to the axially extending part of the flange of the shelland the radially extending part 36 of the flange of the shell 23b alsobeing bent at right angles to the axially extending part 34 of theilange of the shell. A circular ring 38 of natural or synthetic rubberis positioned between and at the juncture of the angularly disposedparts 35 and 37 of the ange of the shell 18b and the angularly disposedparts 34 and 36 of the ange of the shell 2311 to provide a seal toprevent the escape of fluid from the housing formed by the shells 18band 23b. In the assembly of the shells, the axially extending parts 34and 35 are disposed in telescoping relation to elect engagement of theoutwardly directed parts 36 and 37 to thereby compress the rubber ring3S between the anges of the shell 18b and the shell 23b. The radiallyouter edges of the tianges are each radially disposed the same distancefrom the uis of the torque converter so that a plurality of welds 39,provided thereon by puddle or tack welding at circumferentially spacedareas thereof, will securely hold the shells 18b and 23h connected toeach other against relative rotation and movement of the shells 18h and23h away from each in axial direction, the abutting parts 36 and 37 ofthe flanges preventing axial movement of the shells 18h and 2317 towardeach other.

The embodiment of the invention illustrated in FIG. 6 is similar to thatillustrated in FIG. 5 with the exception that the telescoped radiallyinneraxially extending part 4i) of the flange of the shell 18e isprovided with an annular groove 4l receiving an O ring of natural orsynthetic rubber compressed between the telescoping parts of the flangesof the shells 18e and 23h10 prevent any possibility of leakage of thefluid from the housing delined by the shells.

In the embodiments of the invention illustrated in FIGS. 5 and 6, thewelding operation taires place quickly and with a minimum amount of heatbeing generated so that with the small amount of welding applied verylittle distortion, if any, occurs in the parts.

FIGS. 7, 8 and 9 illustrate another embodiment of the invention forassembling two opposed hollowshells 43 and 44 having substantiallysemi-toroidal portions, as shown in FIG. 1. The shell 43 is preferablyformed as an aluminum casting provided with a radially outer annularportion or ange 45 having an annular rib 46 projecting radiallyoutwardly from the outer cylindrical surface 'thereof at itscircumferentially extending edge 47. The shell 44 is provided with aradially outer portion or axially extending tlange 48 in telescopingrelation to the 6i flange 45 and engaging rib 46. As seen moreparticularly in FIG. 8, the rib 46 is provided with a plurality ofcircumferentially spaced notches or recesses 49 in .the radiallyextending surface at one side thereof, for receiving a plurality oftongues 51 entering into the notches 49 during the spinning or rollingoperation of the circumferentially extending end of the flange 48 toprovide a radially inwardly extending annular lip 52 engaging the side50 of the rib 48 to prevent relative axial movement of the shell 44 andthe shell 43 away from each other and to prevent relative rotation ofthe shells. As seen in FIG. 7, the shell 44 is provided with a shoulder53 having an axially extending surface engaging the radially innersurface of the cylindrical ilange 45 of the shell 43. It will be seenthat the abutment of the end of the ange 45 of the shell 43 withtheradially extending portion of the shell 44, in cooperation with the lip51 engaged with the rib 46, prevents relative axial movement of the twoshells. A ring 54 of natural or synthetic rubber is disposed between theflanges 45 and 43 at the juncture of the radially and axially extendingportions of the flange 48 and engages an inclined surface 54a on the endofthe flange 45 and the ring is thereby compressed between the twoshells to prevent leakage of huid between the anges and from `thehousing. The formation of the rib 46 on the shell 43 is related to theflange 48 of the shell 44 so that the abutment of the end of the ange 45ot" the shell 43 against the shell 44 positions the end of the ilange 48to be moved radially inwardly by a rolling or die operation from theposition shown in FIG. 7 and over the side 50 of the rib 46 to engagethe same and to enter the notches 49 in the rib 46, as shown in FIGS. 8and 9.

The embodiment of the invention illustrated in FIG. l() is similar to`that illustrated in FIGS. 7, 8 and 9 with the exception that thecylindrical portion 55a of the cast aluminum shell 55 is provided with arib 56 having an annular groove 57 therein for receiving an O ring 57acompressed between the flange 48 of the shell 44 and the flange 55a ofthe shell 55.

In each of the embodiments of the invention illustrated in FIGS. 7, 8and 9 and FIG. l0, the shoulder 53 on the shell 44 is essential toprevent the shell 43 or 45 from collapsing inwardly during the rollingor die oper-ation anging over the end of the flange 48 of the shell 44to form the lip 52. In each ot-4 these assembly operations, the shell 44and the shell 43 or 45 are required to be pressed together-so that theedge 47 oi the shell 43 or 45 butts tirmly against the shell 44 and theseal ring is compressed a desired amount to prevent leakage of fluid. Itwill be apparent that, in the absence or" the shoulder 53 on the shell44, the shell 43 or 45 might be distorted inwardly during the formingconnecting operation, which would relieve the pressure on the seal ringand possibly permit leakage of the fluid from the housing.

It will be apparent from an inspection of the two embodimentsillustrated in FIGS. 7, 8 and 9 and in FIG. 10, that the two shells areheld tightly secured together against relative axial movement andrelative rotary movement by the assembly operations described.

In the embodiment of the invention of FIG. 1l, another form ofconnection is illustrated `between -a' drive plate 58 and impellercasing 59 providing two opposed shells having substantiallysemi-toroidal portions as shown in FIG. l. The shell 58 has an outercircumferentially extending annular ange 60 surrounding a radiallyextending ange 61 of the shell 59. The flange 60` forms a reduced endportion of the shell 58 to provide a shoulder 62 delining a pocket withthe flange 61, the shoulder abutting the radially extending portion 63of an annular sheet metal stamping or ring 64 of L-section extendingwithin the pocket, the axially extending portion 65 ot the ring havingits edge engaging the side of the ilange 61 of the shell 59, and theedge of the ring portion 63 being seated against the circumferentiallyextending inner surface of the ange 60. The ring 64 thus serves to spacethe shells 58 and 59 so that, in the assembly operation, the end of theflange 60 extends axially beyond the ange 61. As in the embodimentillustrated in FIGS. 7-9, inclusive, the end of the ilange 60 is formedover by a rolling or die operation to form a lip `66 in engagement withthe side of the flange 61 to secure the shells together against axialmovement away from each other and with portions of the lip enteringnotches 67 in the side of the flange 61 to prevent relative rotation ofthe shells. A seal ring 68 of compressibl-e material, such as rubber,and which may be an O ring, is received within the L-shaped ring 64, asshown, is compressed between the ring 64 and the flanges 60 and 61 toprevent leakage of fluid from the connected shells. In the assemblyoperation, when the two shells are pressed together to compress and loadthe rubber seal,l

the rubber seal .bottoms against the ring 64 and through it to theshoulder 62, and while the parts are held in this position, the end ofthe ilange 60 is formed over to lock the two shells together.

Referring to FIG. 12 showing another type of connection between twoshells 69 and 70, the shell 69 has a circumferentially extending annularange 71 in telescoping relation to a flange 72 of the shell '70. The endof the flange 72 is machined at its outer diameter to provide a reducedportion providing a shoulder 74 abutting the edge of the flange 71 toposition the shells in predetermined axial relation to each other. Theend of the flange 71 yis also of reduced diameter to provide a shoulder75 dening a pocket with the end of the flange 72, the shoulder Iabutting the side of a radially extending portion 76 of an annular sheetmetal stamping or ring 77 of L-section. The ring 77 has its axiallyextending portion 78 extending toward and disposed radially inwardly ofthe end of the ange 72. Disposed within and engaging the ring 77 is arubber seal ring 79 in engagement with the ring 77, the end of the ange72 and the inner surface of the lreduced portion of the flange 72.

In the assembly of the shells, the shells are held tightly together withthe shoulder 75 of the flange 71 and the end of the ange 72 compressingthe seal ring 79 a predetermined amount while a welding operation isperformed to provide a plurality of circumferentially spaced welds 80between the flanges 71 `and 72 as shown. The edge of the ange 71 may bebeveled and recesses formed therein and in the flange 71 to providesuiciently large adjacent areas to insure lsatisfactory welds Si)between the flanges to securely connect the shells to each other.

The connections and assembly of the shells illustrated in FIGS. 1-4 and7-11 may be serviced in the eld by service stations and garages byreversely rolling the spunover edge of the telescoping shell allowingthe two shells to be readily disassembled for servicing of the torqueconverter, including replacement of the seal ring, and thereafter thetwo shells may be telescope-d and the edge of the telescoping shell.again either spun or rolled over the telescoped shell to connect theshells together.

If the alternative form of connection is' used, i.e., circumferentiallyspaced spot welds, the two shells can be easily disassembled by removingthe welds by machining about .050 inch of the edges of the telescopingend of the shell, and in FIG. l2, the welds may be removed by machiningthe welds from the `shells and in each case, a new seal ring is theninstalled. Since no distortion occurred originally in the weldingoperation, the shells can then be quickly telescoped again to abut theiroriginal shoulders or engaging parts and thereafter the Weldingoperation to connect the shells can be done with equipment available atany `service station or garage.

It will be apparent from the foregoing description that I havey providedimproved structures and assemblies of shells of duid-containing housingsof hydrodynamic coupling devices, which may ybe of the iluid coupling orhydraulic torque converter types, in which two shells may be readilyassembled and secured together in a manner retaining the original shapesof the shells to provide housings with uniform axial and radialdimensions to satisfy the limited space requirements both diametricallyand axially for ltorque converters and uid couplings as required invarious installations and particularly -in autol motive applications. Inmany cases, it is desirable to dispose the fluid coupling or torqueconverter in a limited diametrical space. The connections of the shellsin accordance with the invention is particularly practical in View ofthe factthat any of the connections require only a slight increase indiametrical space in some instances. This feature is advantageous wherelimited diametrical space'would nia-ke it impossible for housings of thebolted ange design to be utilized.

This application is a -continuation-in-part of a co-pending applicationentitled Hydrodynamic Coupling Devices, Serial Number 509,7l8, tiled May20, 1955 now issued Patent Number 3,024,735, dated March 13, 1962.

While this invention has been described in detail and in severalforms orembodiments, it will be apparent to persons skilled in the art afterunderstanding the irnprovements, that various changes and modificationsmay be made therein in structure and methods of assembly withoutdeparting from the spirit of the scope thereof. It is therefore aimed inappended claim to cover all such changes and modications.

I claim:

In a hydrodynamic coupling device, two opposed sheet metal shells havinghollow portions defining a toroidal uid containing housing, said shellsbeing provided With radially outer telescoping annular portionsprojecting in a common axial direction from the hollow portions of saidshells and projecting in a common radial plane such that a positiveaxial stop means is formed therebetween and such that circumferentialedges of said shells are disposed adjacent each other, seal meansdisposed between `said shells, and a plurality of circumferentiallyspaced means integral with said edges connecting said shells to eachother.

SAMUEL LEVINE, Primary Examiner.

